soo Captain Sabine’s comparison of barometrical and 
In the experiments for determining the height of the hill, 
Newman’s barometer was employed on the summit, and 
Jones’s by the sea. The station of the lower barometer was 
on the outside of a house framed of wood with boarded walls, 
which was constructed for my pendulum experiments ; the 
house was 1 2 feet square, and stood withinside a tent of suf- 
ficient dimensions to admit of passage room between the 
walls of the tent and house ; the barometer was so suspended 
as to be entirely detached from the side of the house, and the 
walls of the tent were unhooked during the ' observations; 
the cistern was 21 feet above the level of half tide. New- 
man’s barometer was suspended beneath the cone on the 
summit of the hill on the 17th of July, and was not removed 
from thence until the afternoon of the 21st, being suffered to 
remain under a temporary protection, which was of course 
removed during the observations ; the cistern was on a level 
with the highest point of the hill, and 44 inches below the 
apex of the cone, which, being the proposed point of mea- 
surement, renders an addition of 21 + 3.66 = 24 .66 feet 
necessary to the result obtained by the barometric difference, 
to give the total height of the cone above half tide. The 
times at which the observations were repeated, were previ- 
ously concerted ; and as the motions of the observer on the 
summit of the hill were visible with a good telescope from 
the Observatory, the simultaneous observation was assured. 
The hygrometer and detached thermometer were used in all 
cases in the open air and in the shade : the hygrometer was 
the recent invention of Mr. Daniell, which is distinguished 
by his name ; the results deducible from the barometric dif- 
ferences, under the observed circumstances of the atmo- 
